Protective cover for a rotating electric machine for a motor vehicle

ABSTRACT

The present invention concerns a protective cover ( 400 ) designed to cover power, filtering and control modules of an electronic assembly for a rotating electric machine for a motor vehicle. Said protective cover ( 400 ) is characterised in that it comprises: openings ( 401, 402, 403, 404 ) designed to generate different cooling air streams (F 1 , F 2 , F 3 , F 4 ) for heat dissipation requirements of each of the power, control and filtering modules; the openings of the protective cover ( 400 ) being distributed into: a first set of openings ( 401 ) designed to be positioned facing the fins of a first heat sink coupled to the power module; a second set of openings ( 402 ) designed to be positioned facing the control module; the two sets of openings ( 401, 402 ) being separated by a barrier wall ( 405 ) so as to create a first radial cooling air stream (F 1 ) for said power module and a second radial cooling air stream (F 2 ) for said control module; and a third set of openings ( 403 ) designed to be positioned facing the fins of a second heat sink coupled to condensers of the too filtering module so as to create a third radial cooling air stream (F 3 ) for said filtering module.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a protective cover suitable forcovering power, filtering and control blocks of an electronic assemblyfor a rotary electric machine for a motor vehicle. The present inventionrelates also to a rotary electric machine comprising such a protectivecover. The invention can be applied particularly but not exclusively inthe field of motor vehicle starter alternators, for example for starteralternators or motor-generators suitable for use with vehicles of themild hybrid type.

TECHNICAL BACKGROUND OF THE INVENTION

In a motor vehicle comprising a heat engine and a rotary electricmachine such as a starter alternator, such a machine comprises, in anon-limiting manner:

-   -   a rotor comprising an inductor in which an excitation current is        conducted; and    -   a stator comprising a multi-phase winding.

The starter alternator operates in motor mode or in generator mode.

This machine is referred to as being reversible.

In alternator mode, also referred to as generator mode, the machinemakes it possible to transform a rotary movement of the rotor driven bythe heat engine of the vehicle into an electric current induced in thephases of the stator. In this case a bridge rectifier connected to thephases of the stator makes it possible to rectify the induced sinusoidalcurrent into a continuous current in order to supply consumers of thevehicle as well as a battery.

By contrast, in motor mode the electric machine acts as an electricmotor making it possible to drive in rotation the heat engine of thevehicle via the rotor shaft. It makes it possible to transform theelectrical energy into mechanical energy: In this case a converter makesit possible to transform a direct current originating from the batteryinto an alternating current in order to supply the phases of the statorin order to turn the rotor.

Control components are used in order to determine the operating mode ofthe rotary electric machine (motor mode or generator mode) via controlsignals.

The starter alternators that integrate a regenerative braking functionand a function of heat engine acceleration assistance, referred to asmild hybrid starter alternators, also integrate filtering componentsthat prevent the power components from interfering with the electricalnetwork of the motor vehicle, generally a network of 48 volts. Thesereversible machines have powers of approximately 8 to 15 kW.

The power components (bridge rectifier and converter), the controlcomponents and also the filtering components generate heat. It is thusnecessary to use a cooling device in order to dissipate this heatemitted by all these components.

Patent FR2847085 describes an electronic assembly comprising the powercomponents and the control components (referred to as control units),the two sets of components being placed as close as possible to oneanother, and a cooling device for cooling this assembly. The coolingdevice comprises:

-   -   a dissipator on which the power and control components are        mounted, the dissipator being arranged on the rear bearing of        the electric machine and comprising fins on its lower face,        which faces the bearing. In addition, there is a free space        between the rotation shaft of the rotor and the dissipator,        through which space air can circulate;    -   the rear bearing comprising radial air outlet holes; and    -   a protective cover comprising openings arranged on the top of        said cover.

Thus, some of the air is sucked laterally into the starter alternatorand flows towards the radial outlet holes of the bearing, while sweepingover the fins of the dissipator, and the remaining air is sucked throughthe openings in the cover and then flows axially along the rotationshaft (via the free space) of the rotor so as to join a flow passagebelow the dissipator. Thus, the assembly of power and control componentsis cooled.

One disadvantage of this prior art lies in the fact that it does notoffer any solution for thermal decoupling between the different blocksof electronic components in relation to their own dissipation needs.Now, in the context of the “mild-hybrid” application, a thermaldecoupling must be effected notably between the power components and thefiltering components. This is because the power components can reachoperating temperatures which can be dangerous for the filteringcomponents and consequently damage them.

In this context, the object of the present invention is to overcome theabove-mentioned disadvantage.

GENERAL DESCRIPTION OF THE INVENTION

To this end, the invention proposes a protective cover suitable forcovering power, filtering and control blocks of an electronic assemblyfor a rotary electric machine for a motor vehicle, wherein saidprotective cover comprises:

-   -   openings suitable for generating different flows of cooling air        for thermal dissipation needs of each of the power, control and        filtering blocks;    -   the openings of the protective cover being divided into:    -   a first set of openings suitable for being positioned facing the        fins of a first dissipator coupled to the power block;    -   a second set of openings suitable for being positioned facing        the control block;    -   the two sets of openings being separated by a separating low        wall so as to create a first radial flow of cooling air for said        power block and a second radial flow of cooling air for said        control block; and    -   a third set of openings that can be positioned facing the fins        of a second dissipator coupled to capacitors of the filtering        block so as to create a third radial flow of cooling air for        said filtering block.

In accordance with another particular feature, the fins of the firstdissipator, the protective cover and the openings of the first set arearranged in such a way as to satisfy the following relationships:

h≧0.5 . ha

H<0.5 . ha, and

D≧0.5 .(d ²−((o−e)/2)²)^(1/2),

-   -   where h is the height of an opening of the protective cover, ha        is the height of a fin of the first dissipator, H is the        distance between the bottom of the protective cover and the        bottom of an opening, D is the distance between the inner edge        of the protective cover and the leading edge of a fin of the        first dissipator, d is an inter-fin space separating two        adjacent fins of the first dissipator, o is the width of an        opening and e is the thickness of a fin.

Thus, by virtue of the various openings dedicated to the various blocksand by virtue of the coupling of some openings with dedicateddissipators, the protective cover makes it possible to provide coolingadapted and optimized for the thermal dissipation needs of each block ofcomponents (power, control, filtering) thanks to the creation ofspecific flows of air for cooling each block.

In accordance with non-limiting embodiments, the protective cover mayalso comprise one or more additional features selected from thefollowing:

-   -   the openings of the first set of openings, of the second set of        openings and of the third set of openings of the protective        cover are lateral, and the openings of the first set of openings        and of the second set of openings are arranged in line with the        fins of the first dissipator.    -   the protective cover also comprises a fourth set of openings        that are arranged on the top of said cover and that can be        positioned above capacitors of the filtering block so as to        create a fourth axial flow of cooling air for the filtering        block.

Also proposed is a rotary electric machine comprising:

-   -   a rotor;    -   a stator coupled to said rotor and comprising a plurality of        phases;    -   an electronic assembly comprising:        -   a power block, a filtering block and a control block, said            power block of said electronic assembly being able to be            connected to the phases of said stator, and        -   a protective cover as described briefly above;    -   a rear bearing supporting said stator; and    -   a fan situated in proximity to the rear bearing.

In accordance with a non-limiting embodiment, said rotary electricmachine is a starter alternator.

In accordance with a non-limiting embodiment, said starter alternatorcomprises a regenerative braking function and an acceleration assistancefunction.

BRIEF DESCRIPTION OF THE FIGURES

The invention and different applications thereof will be betterunderstood upon reading the following description and examining theaccompanying figures.

FIG. 1a shows an exploded perspective view of a first non-limitingembodiment of an electronic assembly for a rotary electric machine for amotor vehicle comprising a protective cover according to the invention;

FIG. 1b shows an assembled perspective view of the electronic assemblyof FIG. 1 a;

FIG. 2 shows a plan view of a power block of the electronic assembly ofFIG. 1;

FIG. 3a shows a perspective view of a power module of the power block ofFIG. 2;

FIG. 3b shows a perspective view of an excitation module of the powerblock of FIG. 2;

FIG. 4 shows a perspective view of a first dissipator coupled to thepower block of FIG. 2;

FIG. 5 shows a view from below of the first dissipator of FIG. 4;

FIG. 6 shows a profile view of the first dissipator of FIGS. 4 and 5;

FIG. 7 shows an assembled perspective view of the power block of FIG. 2with the first dissipator of FIGS. 4 to 6;

FIG. 8 shows a perspective view of a filtering block of the electronicassembly of FIG. 1;

FIG. 9 shows a view of a second dissipator coupled to the filteringblock of FIG. 8;

FIG. 10 shows a non-limiting embodiment of assembly of the filteringblock of FIGS. 8 and 9 with the first dissipator of FIGS. 4 to 6 withoutthe capacitors;

FIG. 11 shows the embodiment of assembly of FIG. 10 with the capacitors;

FIG. 12 shows an enlarged view of a part of the assembly of FIG. 11;

FIG. 13 shows an exploded view of the assembly of the filtering block ofFIG. 11;

FIG. 14 shows a perspective view of a control block of the electronicassembly of FIG. 1;

FIG. 15 shows a profile view of the control block of FIG. 14;

FIG. 16 shows a view from below of the control block of FIGS. 14 and 15;

FIG. 17 shows a perspective view of a protective cover of the electronicassembly of FIG. 1, according to the invention;

FIG. 18 shows a profile view of the protective cover of FIG. 17;

FIG. 19 shows a plan view of the protective cover of FIGS. 17 and 18;

FIG. 20 is a diagram explaining the air flows generated by lateralopenings of the protective cover of FIGS. 17 to 19;

FIG. 21 is a diagram explaining the openings of the protective cover ofFIGS. 17 to 19 which are arranged facing the fins of the firstdissipator of FIGS. 4 to 6 and of the second dissipator of FIG. 9; and

FIG. 22 shows a rotary electric machine comprising the electronicassembly of FIG. 1.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Elements that are identical, either in structure or in function,appearing in different figures will keep the same reference signs,unless specified otherwise.

The electronic assembly 10 for a rotary electric machine is describedwith reference to FIGS. 1 to 22. The rotary electric machine, in anon-limiting example, is a starter alternator for use in a vehicle ofthe mild hybrid type. The rotary electric machine in this type ofapplication is used not only for electric generation and starting of theheat engine (with “stop & go” or “stop/start” functionality), but alsofor regenerative braking, traction at low speed of the vehicle, andtorque assistance of the heat engine.

As illustrated in FIG. 1, in accordance with a non-limiting embodiment,the electronic assembly 10 comprises:

-   -   electronic component blocks 100, 200, 300, the blocks having        different thermal dissipation needs, the blocks being:        -   a power block 100;        -   a filtering block 200;        -   a control block 300;        -   a device 10′ for cooling said blocks 100, 200, 300, said            cooling device 10′ comprising:            -   a protective cover 400 suitable for covering the power,                filtering and control blocks 100, 200, 300, said                protective cover comprising openings 401, 402, 403, 404                suitable for generating different flows of cooling air                F1, F2, F3, F4 for the thermal dissipation needs of each                of the power 100, control 300 and filtering 200 blocks;            -   and cooling elements 101, 201, 301 coupled to said                protective cover 400.

As will be seen in detail hereinafter, thanks to the structure of theelectronic assembly in separate blocks, the creation of the differentair flows for cooling the different blocks, and the coupling between thecooling elements to the openings of the cover, a thermal decoupling isobtained between the different blocks and the cooling of each block isoptimized. Targeted cooling is obtained for each block, each blockhaving different operating temperatures and thus having differentthermal dissipation needs. An improved cooling of the electronicassembly is thus obtained.

In a non-limiting embodiment,

-   -   a first cooling element is a first dissipator 101 provided with        a plurality of fins 1011 coupled to said power block 100;    -   a second cooling element is a second dissipator 201 provided        with a plurality of fins 2011 coupled to capacitors 202 of said        filtering block 200;    -   the control block 300 is arranged on a first plane P1 parallel        to a second plane P2 on which is mounted the power block 100 so        as to allow passage of a flow of cooling air F2 between the two        blocks 100, 300;    -   the openings of the protective cover 400 are divided into:        -   a first set of openings 401 that can be positioned facing            the fins of the first dissipator 101;        -   a second set of openings 402 that can be positioned facing            the control block 300;        -   the two sets of openings 401, 402 being separated by a            separating low wall 405 so as to create a first radial flow            of cooling air F1 for said power block 100 and a second            radial flow of cooling air F2 for said control block 300;            and        -   a third set of openings 403 that can be positioned facing            the fins of the second dissipator 201 so as to create a            third radial flow of cooling air F3 for said filtering block            200.

The different elements of the power electronic assembly and coolingdevice 10 thereof, as well as the different air flows generated, will bedescribed in greater detail hereinafter.

Power Block

FIG. 2 represents a plan view of the power block 100. In thisnon-limiting example, the power block 100 comprises three power modules1001 and an excitation module 1002.

The power modules 1001 comprise electronic switches, such as MOSFETtransistors by way of a non-limiting example, the switches of a modulebeing intended to provide a bridge rectifier/converter branch for aphase of the rotary electric machine. A non-limiting example of a powermodule 1001 is shown in FIG. 3a . It comprises interconnection pins 103described later in the description.

The excitation module 1002 makes it possible to supply the coil of therotor of said machine, said module conventionally comprising MOSFETtransistors and diodes making it possible to determine the current inthe rotor.

A non-limiting example of an excitation module 1002 is shown in FIG. 3b. It comprises interconnection pins 103′ described later in thedescription. A magnetic sensor 1003 can also be seen which makes itpossible to determine the position of the rotor.

Since the power modules 1001 and the excitation module 1002 are sourcesof heat, it is necessary to cool them.

To this end, the cooling device 10′ comprises a first cooling element,which is a first dissipator 101 (also referred to as a power blockdissipator) provided with a plurality of fins 1011 coupled to the powerblock 100. The latter are in a non-limiting embodiment arrangedsubstantially radially under the power block 100. They areconventionally made of aluminum.

The fins 1011 of the first dissipator 101 are represented in theperspective view of FIG. 4 and the profile view of the power blockdissipator 101 in FIG. 6.

These fins provide a large surface area for exchange with the airpassing through the electronic assembly.

Thus, as will be seen hereinafter, the cooling of the block 100 will beoptimized thanks to the fins of the dissipator 101.

In addition to the power 1001 and excitation 1002 modules, the powerblock 100 comprises conductive tracks, which allow the passage ofcurrent into the components. These conductive tracks are also sources ofheat and must be cooled.

It should be noted that the first dissipator 101 also comprises:

-   -   a plurality of mounting tabs 1013 as represented in FIGS. 4 to        6, said tabs making it possible to fix the control block 300.        These mounting tabs 1013 serve as spacers between the two blocks        100 and 300. The control block 300 is thus arranged on a plane        parallel to that of the power block 100. In a non-limiting        example, four tabs are used;    -   at least two mounting tabs provided with orifices 1014 as        illustrated in FIGS. 4 and 5, these tabs making it possible to        fix the filtering block 200. In a non-limiting example, two        mounting tabs are used. The filtering block is described        hereinafter;    -   a plurality of mounting orifices 1015 as represented in FIGS. 4        to 6, said orifices making it possible to fix the power block        100. In a non-limiting example four orifices are used.

Filtering Block

The filtering block 200 is illustrated in FIGS. 8 to 13.

As illustrated in FIGS. 8 and 9, the filtering block 200 comprises aplurality of capacitors 202 intended to filter the interferenceoriginating from the power components (power modules 1001 inparticular).

In order to cool the capacitors 202, the cooling device 10′ comprises asecond cooling element, which is a second dissipator 201 (also referredto as a filtering block dissipator) provided with a plurality of fins2011, said dissipator being coupled to the capacitors 202.

These fins provide a large surface area for exchange with the airpassing through the electronic assembly. Thus, as will be seenhereinafter, the cooling of the block 200 and therefore of thecapacitors 202 will be optimized thanks to the fins of the dissipator201.

In a non-limiting embodiment, the second dissipator 201 is coupled tothe capacitors 202 of the filtering block 200 by means of a resin 2013.Thus, the resin makes it possible not only to hold said capacitors 202in the dissipator, but also to have good evacuation of the calories ofthe capacitors towards said dissipator 201.

In this embodiment in which the machine 1 (FIG. 22) is a machine of thestarter alternator type operating under a continuous voltage of 48volts, voltage potentials B+ and B− are present in the machine 1 andcorrespond respectively to +48 V and to 0 V of the 48 volts. It shouldbe noted here that B− (0 V) and the general ground potential of thevehicle (referenced M− in FIG. 22) are electrically insulated in themachine 1, this being a general ground that is conventionally connectedto the negative electrical terminal of the battery or batteries of thevehicle and also to the body of the latter and that is also connected inthe machine 1 to the rear bearing 40 thereof, on which the electronicassembly 10 is fixed. Electrical insulation is thus provided between theelectronic assembly, of which the electric ground is at B−, and the rearbearing 40 connected to M−. Of course, an electrical connection can beestablished between B− and M− in the electric circuit of the vehicle,but in this embodiment this is not provided in the machine 1.

With reference in particular to FIGS. 8 and 9, B+ is connected to theelectric circuit of the vehicle via an insulated electrical terminal 205of B−. B− is connected to the electric circuit of the vehicle via anelectrical terminal 206 electrically connected to the metal parts (inparticular dissipators) of the power block 100 and of the filteringblock 200 and the ground of the control block 300. An electricalconnection tongue 207 is also shown in FIGS. 8 and 9, and this tongue207 ensures the interconnection of B+ between the filtering block 200and the power block 100.

The power block 100 and the filtering block 200 thus both compriseconductive tracks of positive and negative polarities connectedrespectively to the potentials B+ and B−. These conductive tracks allowthe passage of current through the electronic components of thedifferent blocks 100, 200.

At the power block 100, the first dissipator 101 is connected to theground B−.

As will be seen hereinafter, thanks to the combination 500 (or group orsub-assembly) shown in FIG. 1a between two blocks of electroniccomponents having different thermal dissipation needs, said blocks beingthe power block 100 and the filtering block 200, and with the aid inparticular of thermal and electrical insulation means and a singleconductive element, an electrical connection of B− between the powerblock 100 and the filtering block 200 is obtained alongside electricalinsulation of this B− with respect to the M− of the rear bearing 40, aswell as a strong thermal resistance, which makes it possible to obtain agood thermal decoupling between the power block 100 and the filteringblock 200.

The combination 500 (or group or sub-assembly) is illustrated in FIG. 1a, and the electrical, thermal and mechanical connections of such acombination 500 are illustrated in FIGS. 11 to 13. In the latterfigures, the power block 100 has not been shown in order to providegreater clarity.

Thus, in a non-limiting embodiment, the electrical, thermal andmechanical assembly of the combination 500, between the blocks 100 and200, and the mounting thereof on the rear bearing 40 of the machine isensured at two mounting points PM1 and PM2 (FIG. 11). At a firstmounting point PM1 shown in FIGS. 12 and 13 in particular, this assemblyis provided by means of:

-   -   a mounting screw 204;    -   an electrically conductive element 104 at potential B−, a first        end 1040 of which is in direct contact, via an upper face, with        a mounting tab of the filtering block 200, on a lower face of        said tab of the block 200, and a second end 1041 of which is in        direct contact, via an upper face, with a mounting tab of the        power block 100, on a lower face of said tab of the block 100,        said tabs of block 200 and of block 100 being formed by        extensions of the dissipators 201 and 101 respectively;    -   a thermal insulator 105 arranged between:        -   said tab of the block 100, which is an extension of the            first cooling element 101, which is the first dissipator 101            provided with a plurality of fins 1011 and coupled to said            power block 100; and        -   a lower face of said conductive element 104;    -   a first electrical insulator 106 arranged between said        conductive element 104 and the rear bearing 40 of the rotary        electric machine; and    -   a second electrical insulator 106′ arranged between a head of        the mounting screw 204 and an upper face of said tab of the        filtering block 200.

The functions of the conductive element 104, of the thermal insulator105 and of the electrical insulators 106 and 106′ will be explainedbelow.

In order to connect the power block 100 and the filtering block 200 atthe same potential B−, in a first non-limiting embodiment, theconductive element 104 is used as illustrated in FIGS. 11 to 13. In anon-limiting embodiment said conductive element is a busbar of U-shapein general.

It is pointed out that a busbar is a shaped plate of copper or aluminum.In a non-limiting embodiment it may comprise an additional tinning so asto prevent oxidation of the copper.

This busbar 104 is arranged between the dissipator of the power block101 and the dissipator of the filtering block 201, as illustrated inFIG. 12, so as to create a junction between the two blocks 101 and 201.The busbar thus acts as an electrical conductor and has a negativepolarity B− by the direct contact thereof with the tabs of the blocks100 and 200.

As illustrated in FIGS. 10 to 13, the first dissipator 101 and thesecond dissipator 201 comprise respectively mounting tabs provided withmounting orifices 1014, 2014 suitable for cooperation with one another.

As illustrated in FIG. 13 which shows an exploded view of FIG. 11, thesecond dissipator 201 comprises mounting orifices 2014 that are disposedopposite the above-described mounting orifices 1014 of the firstdissipator 101, and the mounting screws 204 are inserted into thesemounting orifices 1014, 2014 and are screwed onto the rear bearing 40,thus ensuring a mechanical fixing of the electronic assembly 10 onto therear bearing 40 of the machine.

This embodiment utilizing the busbar 104 and the thermal insulator 105makes it possible to minimize the thermal exchanges compared withanother embodiment in which the two dissipators 101 and 201 would beplaced in direct contact by the metal conductive parts thereof. In fact,in the described embodiment, the metal conductive part of the busbar isdimensioned in section and contact surface so as to minimize the thermalexchanges between the power block 100 and the filtering block 200, whileat the same time allowing an electrical conduction needed between blocks100 and 200. The thermal conduction between the dissipators 101 and 201is thus minimized knowing that the thermal and electrical conductionbetween the dissipators 101 and 201 can be provided only through thebusbar 104 due to the presence of the thermal (and electrical) insulator105. The thermal resistance between the dissipators 101 and 201 is thusincreased, which reduces the thermal exchanges and allows a good thermaldecoupling between the power block 100 and the filtering block 200, thetwo blocks 100 and 200 operating in different temperature ranges.

It should be noted that, due to the presence of capacitors 202, thefiltering block 200 must not reach excessively high temperatures (above150° C. by way of a non-limiting example), otherwise the capacitors 202could be subjected to deterioration. Now, the power block 100 for itspart can exceed 150° C. due to the presence of MOSFET switches, whichrelease a lot of heat. It is thus necessary to carry out a thermaldecoupling between the filtering block 200 and the power block 100whilst allowing the passage of current between the two blocks.

The electrical insulators 106 and 106′ allow the electrical insulationbetween the dissipators 101 and 201 at B− and the rear bearing 40 at M−of the rotary electric machine 10, knowing that the mounting screw 204screws into the metal part of the rear bearing 40 of the machine. Theelectrical insulators 106 and 106′ prevent any contact between themounting screw 204 and the dissipators 101, 201 and busbar 104.

In a non-limiting example, the insulator 105 is a washer made of aplastic of low thermal conductivity, and the insulators 106 and 106′ arewashers made of a plastic of low electrical conductivity. These washersare illustrated in FIG. 12 which is an enlarged view of the dotted linepart of FIG. 11.

It should be noted that the orifices 1014, 2014 of the mounting tabsmust have a diameter that is sufficiently large compared to that of themounting screw 204 to avoid any contact thereof with the inner walls ofthe orifices 1014, 2014 and to allow the insertion of a surroundingcollar (not shown) of the insulating washers 106, 106′ into the spacebetween the circular edges/inner walls of the orifices 1014, 2014 andthe surface of the shank of the mounting screw 204, this surroundingcollar guaranteeing the impossibility of such contact. These means makeit possible to obtain the desired mounting with electrical insulationbetween the metal parts of the dissipators 101/201 and the rear bearingof the machine.

A second mounting point PM2, at the insulated electrical terminal 205 isused for the electrical, thermal and mechanical assembly of thecombination 500 between the blocks 100 and 200 and for the mountingthereof on the rear bearing 40 of the machine. Since the means used aresubstantially the same as those used at the first mounting point PM1,these will not be detailed here.

Control Block

The control block is illustrated in FIGS. 14 to 16. As illustrated inthe perspective view of FIG. 14, the control block 300 comprisescomponents 302 for controlling the rotary electric machine and inparticular the setting of the machine by controlling the power modules1001 of the power block 100. Since the components 302 are known to aperson skilled in the art, they are not described in the rest of thedescription.

The control block is composed of a printed circuit board (PCB) on whichthe control components 302 are mounted.

The control block 300 is thermally separated from the power block 100.

Thus, the control function of the power modules is not located in thelatter. To this end, in a non-limiting embodiment, the control block 300is arranged on a first plane P1 parallel to a second plane P2 on whichthe power block 100 is mounted so as to allow a passage of a flow ofcooling air F2 between the two blocks 100, 300. Thus, by creating aspace between the two blocks 100 and 300, this makes it possible toguide the air between the two blocks. The whole is thus cooled whilstcreating a thermal decoupling between the two blocks. The creation ofthis flow of air will be explained in the description below.

In a non-limiting example the control block 300 is mounted above thepower block 100 by means of mounting orifices 304 coupled to themounting tabs 1013 of the first dissipator 101, which serve as spacersas seen before.

In order to communicate therebetween, the power block 100 and thecontrol block 300 are connected to one another by means ofinterconnection pins, respectively 103, 103′, as illustrated in FIGS. 2,3, 4. These interconnection pins 103-103′ are inserted respectively intospaces provided 303-303′ in the control block, as illustrated in FIG.14. FIG. 15 is a profile view of the control block 300.

FIG. 16 shows the control block 300 in a view from below. The spaces303-303′ for inserting the interconnection pins 103-103′ describedpreviously are shown, as are the mounting orifices 304 describedpreviously.

Since each pin has a small section, the possibility of heat exchangebetween the two blocks is minimized. It should be noted that the powermodules 1001 comprise a first set of interconnection pins 103, which aresignal pins.

In addition, the excitation model 1002 comprises interconnection pins103′ that make it possible to send measurement signals and controlsignals. Thus, said interconnection pins make it possible to control theexcitation current of the rotor and to check said current, to sendsensor signals in order to check the position of the rotor, to raise thetemperature of the machine, etc.

It will also be noted that, during operation thereof, some components ofthe PCB will heat up and cause the temperature of the PCB plate to rise.Also, in order to cool this PCB plate, the cooling device 10′ in anon-limiting embodiment comprises a third cooling element, which is athird dissipator 301 (also referred to as the control block dissipator)provided with a plurality of fins 3011 coupled to the control block 300as illustrated in the view from below of FIG. 16.

Thus, by inserting a dissipator into the PCB housing, more precisely onthe lower face of the PCB, it is possible to also use the same flow ofcooling air F2 that allows the thermal decoupling between the controlblock 300 and the power block 100 in order to extract the caloriesintroduced by the components of the PCB.

In non-limiting examples the third dissipator 301 is coupled tocomponents of the control block 300 by means of a resin, a metal strip,a gap filler or a gap pad.

Protective Cover

As will be seen hereinafter, the flows of cooling air suitable for eachdifferent thermal dissipation block are generated and oriented on thedifferent blocks by means of the protective cover. Some of these flowsof air will thus sweep over the fins of the different dissipatorscoupled to the different blocks and will thus optimize the cooling ofsaid blocks, said fins increasing the surface area of dissipation ofcomponents that heat up.

The protective cover 400 is illustrated in FIGS. 17 to 19.

As illustrated in FIGS. 17 and 18, the protective cover 400 comprisesopenings that are divided into:

-   -   a first set of openings 401 that can be positioned opposite the        fins of the first dissipator 101;    -   a second set of openings 402 that can be positioned facing the        control block 300;    -   the two sets of openings 401, 402 being separated by a        separating low wall 405 so as to create a first radial flow of        cooling air F1 for said power block 100 and a second radial flow        of cooling air F2 for said control block 300; and    -   a third set of openings 403 that can be positioned opposite the        fins of the second dissipator 201 so as to create a third flow        of cooling air F3 for said filtering block 200.

The fan 50 of the electric machine sucks in air in order to cool thestator of said machine. This air is sucked in laterally via the openings401, 402, 403 of the protective cover and then flows towards and throughsaid openings. From this sucked-in air, due to the presence of the threetypes of openings 401, 402 and 403 and of the separating low wall 405,three different flows of air are created respectively, F1, F2 and F3.

In this non-limiting embodiment, the separating low wall 405 whichserves as separation between the first set of openings 401 and thesecond set of openings 402 consists of the material of the cover 400.

First Set of Openings 401

The first set of openings 401 makes it possible to generate the firstflow of air F1. Since this first flow of air F1 is sucked in by the fantowards the base, it sweeps over the lower surface of the power block100 (via the first dissipator 101). As can be seen in the explanatorydiagram of FIG. 20, the first flow of air F1 will flow radially throughthe first set of openings 401 and will sweep over the dissipatorelements, that is to say the fins 2011 of the first dissipator 101 overtheir entire length, before exiting axially towards the electric machine1, that is to say along the axis AZ of the rotor. The power block 100 isthus cooled by the cooling of the first dissipator 101 via the fins.

Second Set of Openings 402

The second set of openings 402 makes it possible to generate the secondflow of air F2. As can be seen in the explanatory diagram of FIG. 20,this second flow of air F2 flows through the second set of openings 402and radially beneath the lower surface of the control block 300, beforeexiting axially along the axis AZ. The control block 300 is thus cooled.

A good thermal decoupling between the two blocks 100 and 300 is obtainedby this separation of the flow of cooling air into a first flow F1 and asecond flow F2 having different flow paths.

It should be noted that in the non-limiting embodiment in which thethird dissipator 301 is present, the cooling of the components of thecontrol block 300 by the flow of air F2 is optimized because said flowF2 will sweep over the fins 3011 of said dissipator 301. The extractionof the calories introduced by some components of the PCB housing thatheat up is thus improved.

In a non-limiting embodiment, the openings of the first set of openings401 and of the second set of openings 402 of the protective, cover 400are lateral and are arranged in the same direction as the fins of thefirst dissipator 101. Thus, since the openings in the protective coverare arranged in the same direction as the fins of the first dissipator101, that is to say vertically here, the flow of air that passes throughthe openings and that will sweep over the fins is greater than if theopenings were in a different direction.

Thus, by producing two sets of openings 401, 402 over the height of theprotective cover 400, instead of a single set, it is possible to betterchannel the incoming flow of air. Furthermore, the positioning of thelow wall 405 between the two sets of vertical openings 401, 402 makes itpossible to obtain two flows of air for respectively cooling the powerblock 100 and the filtering block 200.

In order to optimize the coupling between openings in the cover/fins ofthe first dissipator 101, it is necessary for these openings to becorrectly positioned with respect to the fins of the first dissipator101.

With reference more particularly to FIGS. 20 and 21, the fins of thefirst dissipator 101, the protective cover 400 and the openings of thefirst set of openings and/or of the second set of openings 401, 402 arearranged so as to satisfy the following relationships:

h≧0.5 . ha   (1)

H<0.5 . ha, and   (2)

D≧0.5 .(d ²−((o−e)/2)²)^(1/2)   (3)

where h is the height of the cover opening, ha is the height of the fin,H is the distance between the base of the cover and the base of theopening, D is the distance between the inner edge of the cover and theleading edge of the fin, d is an inter-fin space separating two adjacentfins, o is the width of a, cover opening and e is the thickness of afin.

The relationships (1) to (3) above have been determined by the inventiveentity by means of tests aiming to determine an arrangement that offersan optimum of cooling. The relationship (1) in particular makes itpossible to guarantee that the cover opening section Soc is sufficientlygreater than the section of the inter-fin channel Sca.

Third Set of Openings 403

The third set of openings 403 makes it possible to generate the thirdflow of air F3. This flow of air will flow radially through the thirdset of openings 403 and will sweep over the dissipator elements, that isto say the fins of the second dissipator 201 over their entire length,before exiting axially towards the electric machine, that is to sayalong the axis AZ of the rotor.

In a non-limiting embodiment the openings of the third set of openings403 are lateral and are arranged in the same direction as the fins ofthe second dissipator 201.

Thus, since these openings in the protective cover are arranged in thesame direction as the fins of the second dissipator 201, that is to sayvertically here, the flow of air that passes through the openings andthat will sweep over the fins is more significant than if the openingswere in a different direction.

This therefore makes it possible to obtain a large surface area ofexchange with the third flow of air F3 and therefore to cool thefiltering block 200, and in particular the capacitors 202, all the more.

Fourth Set of Openings 404

In a non-limiting embodiment the protective cover 400 also comprises afourth set of openings 404 that are arranged on the top of said cover400 (as illustrated in FIG. 17 or 19) and that can be positioned abovecapacitors 202 of the filtering block 200 so as to create a fourth flowof cooling air F4 for the filtering block 200.

As illustrated in FIGS. 17 and 18, this fourth flow

F4 will flow axially through the fourth set of openings 404, that is tosay parallel to the axis AZ of the rotor, and will sweep over thecapacitors 202, but also the dissipator elements, that is to say thefins 2011 of the second dissipator 201, before exiting towards theelectric machine.

An axial flow of air also cooling the filtering capacitors 202 is thuscreated.

Thus, the fins of the second dissipator 202 receive a radial flow of air23 and an axial flow of air F4, which makes it possible to increase thesurface area of exchange with the air and therefore obtain an optimalflow of air (composed of two flows of air) over the fins. Thanks to thisoptimization of thermal exchange, the capacitors are thus cooled well.

It should be noted that another function of the protective cover 400 isto protect the electronic assembly against mechanical attacks, such asthe intrusion of a screw or of a mechanical tool for example, etc. Theopenings 401, 402, 403 and also 404 must also be dimensioned so as toavoid such mechanical attacks and so as to observe a maximum width ldetermined in accordance with the desired protection against saidattacks. The value l is thus dictated by the degree of protectiondesired for the starter alternator against the penetration of foreignbodies, which are in particular solid (also referred to as IPprotection).

Thus, the electronic assembly 10 described above makes it possible tooperate the starter alternator 1. The latter comprises, as illustratedin FIG. 22:

-   -   a rotor (not shown in FIG. 22);    -   a stator 30 coupled to said rotor and comprising plurality of        phases;    -   an electronic assembly 10 in accordance with any one of the        preceding features, the power block 100 of said electronic        assembly 10 being suitable for being connected to the phases of        said stator 30;    -   a rear bearing 40 supporting said stator 20; and    -   a fan 50 arranged in the proximity of the rear bearing 40.

Of course, the description of the invention is not limited to theapplication, to the embodiments, or to the examples described above.

Thus, the present invention applies to any type of reversiblemulti-phase rotary electric machine, such as starter alternators, drivenby belt for example or integrated, and in particular for hybridapplications.

Thus, in another non-limiting exemplary application, the starteralternator is full hybrid and makes it possible to drive the motorvehicle by means of the electric motor alone (generally duringstart-up), or by means of the heat engine alone (generally when thespeed rises), or by the engine and the electric motor at the same time(for example in order to obtain stronger acceleration). The battery thatsupplies the electric motor recovers energy by regenerative braking.

Thus, the invention described in particular has the followingadvantages:

-   -   it allows a thermal decoupling between the control block and the        power block thanks to:    -   the mechanical assembly thereof: the two blocks are arranged on        two parallel planes with a space allowing the passage of a flow        of air, and    -   the electrical assembly thereof: the two blocks are connected        via the interconnection pins, which minimize the possibility of        thermal exchange between the two blocks, the thermal exchange        surface area being very low;    -   the second flow of air passing between the control block and the        power block;    -   it allows a thermal decoupling between the power block and the        filtering block thanks to:    -   the thermal insulation of the second dissipator and the first        dissipator via the insulating washers;    -   the electrical assembly thereof: the two blocks are connected        via a single busbar, which minimizes the possibility of thermal        exchange between the two blocks, the conductive part being        reduced.    -   it allows an optimization of the cooling of the components of        the electrical assembly thanks to:    -   the structure in separate operational blocks (power block,        filtering block, control block), the blocks having different        operating temperatures (medium and maximum) as well as different        dissipation needs;    -   the creation of flows of air dedicated to each functional block        via the structure of the protective cover of the cooling device:        -   the presence of the separating low wall between two sets of            openings;        -   the openings for orienting the entry of air into the            electronic assembly;        -   the shape and positioning of these openings with respect to            the cooling fins of the first and second dissipators;    -   the coupling of the cooling elements of the cooling device, that        is to say different dissipators, with the different functional        blocks, the fins of said dissipators making it possible to        increase the surface area for exchange with air in order to        evacuate the calories;    -   the passage of a radial flow of air and of an axial flow of air        in order to avoid an overheating of the capacitors and thus        prevent damage thereto;    -   the resin which allows a good evacuation of the calories of the        capacitors towards the second dissipator;    -   the presence of openings in the first dissipator for cooling the        busbars.

1. A protective covering suitable for covering power, filtering andcontrol blocks of an electronic assembly for a rotary electric machinefor a motor vehicle, wherein said protective cover comprises: openingssuitable for generating different flows of cooling air for thermaldissipation needs of each of the power, control and filtering blocks;the openings of the protective cover being divided into: a first set ofopenings suitable for being positioned facing the fins of a firstdissipator coupled to the power block; a second set of openings suitablefor being positioned facing the control block, the two sets of openingsbeing separated by a separating low wall so as to create a first radialflow of cooling air for said power block and a second radial flow ofcooling air for said control block; and a third set of openings bepositioned facing the fins of a second dissipator coupled to capacitorsof the filtering block so as to create a third radial flow of coolingair for said filtering block.
 2. The protective cover as claimed inclaim 1, wherein the openings of the first set of openings, of thesecond set of openings and of the third set of openings of theprotective cover are lateral, and the openings of the first set ofopenings and of the second set of openings are arranged in line with thefins of the first dissipator.
 3. The protective cover as claimed inclaim 1, wherein the fins of the first dissipator, the protective coverand the openings of the first set are arranged in such a way as tosatisfy the following relationships:h≧0.5 . haH<0.5 . ha, andD≧0.5 .(d ²−((o−e)/2)²)^(1/2), where h is the height of an opening ofthe protective cover, ha is the height of a fin of the first dissipator,H is the distance between the bottom of the protective cover and thebottom of an opening, D is the distance between the inner edge of theprotective cover and the leading edge of a fin of the first dissipator,d is an inter-fin space separating two adjacent fins of the firstdissipator, o is the width of an opening, and e is the thickness of afin.
 4. The protective cover as claimed in claim 1, wherein theprotective cover further comprises a fourth set of openings that arearranged on the top of said cover and positioned above capacitors of thefiltering block so as to create a fourth axial flow of cooling air forthe filtering block.
 5. A rotary electric machine comprising: a rotor; astator coupled to said rotor and comprising a plurality of phases; anelectronic assembly comprising: a power block, a filtering block and acontrol block, said power block of said electronic assembly being ableto be connected to the phases of said stator, and a protective cover asclaimed in claim 1; a rear bearing supporting said stator; and a fansituated in proximity to the rear bearing.
 6. The rotary electricmachine as claimed in claim 5, wherein said rotary electric machine is astarter alternator.
 7. The rotary electric machine as claimed in claim6, wherein said starter alternator comprises a regenerative brakingfunction and an acceleration assistance function.